Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
  • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
  • G01S5/14—Determining absolute distances from a plurality of spaced points of known location
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
  • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
  • G01S5/0295—Proximity-based methods, e.g. position inferred from reception of particular signals

Definitions

• This invention relates to real-time methods and systems for locating a mobile object or person in a tracking environment and, in particular, to real-time methods and systems for locating a mobile object or person in a tracking environment in which a plurality of sensors are located.
• Battery-operated (i.e. active) tracking badges and tags often emit radio-frequency (RF) and other signals such as ultrasonic or infrared (IR) signals. These signals are used to precisely establish the real-time location of mobile assets and people to which the badges and tags are affixed.
• RF radio-frequency
• IR infrared
• Typical fire rates for IR are set at every 3 seconds on badges and 9 seconds for asset tags.
• RF signals are typically set at every 12 seconds on each type of badge. Firing rates can be preselected. Since some tags feature a motion sensor, the tag will go to "sleep" (fire less often to save on battery life) when there is no movement.
• Recent asset tag batteries may last up to three years, depending on their preselected firing rate. Patient/personnel tags have a shorter battery life because they are in use and firing signals more frequently than asset tags, consequently, badge batteries typically last up to 18 months. In any event, however, battery-operated tracking tags have a fixed energy budget.
• U.S. patent publication 2008/0218351 discloses an RFID tag conservation method and system for active multi-modal RFID tags, illuminator/tag/reader systems, circuit architecture and operational algorithms for battery power conservation that extends tag battery life from a typical 6 months to > 5 years.
• the system is particularly useful in asset and person tracking/inventory systems where power conservation is critical.
• the tag is configured with a microprocessor operational instruction set algorithm, modifiable on the fly via RF or IR, to synchronize a periodic tag awaken/sense envelope that overlaps the illuminator trigger pulse cycle and puts the tag into deep power conservation sleep for N periods of illuminator cycles.
• the tag When the tag sees an illuminator signal with a different ID, or no illuminator signal at all, it transmits that anomaly via RF to a reader. This means the object or person with which the tag is associated has been moved out of the original illuminator field of view, permitting near real-time investigation and tracking.
• An object of at least one embodiment of the present invention is to provide an improved real-time method and system for locating a mobile object or person in a tracking environment.
• a real-time method of locating a mobile object or person in a tracking environment in which a plurality of sensors are located includes providing a tracking tag wearable by the person or attachable to the object.
• the method further includes modulating a first carrier signal with a first packet including a first set of data to obtain a modulated first signal.
• the method still further includes transmitting from the tag to a sensor nearest the tag the first signal.
• the first signal contains the first packet and has a first precision and a first range within the environment.
• the method further includes repeating the steps of modulating and transmitting until a modulated second signal is received at the tag from the nearest sensor within a time period after the step of transmitting.
• the second signal contains a second packet including a second set of data and has a second precision and a second range within the environment.
• the method still further includes receiving the second signal at the tag within the time period.
• the method further includes demodulating the second signal to obtain the second packet.
• the method still further includes determining location of the tag within the environment based on the second packet of the received demodulated second signal.
• At least a portion of the second set of data may uniquely identify the nearest sensor.
• the first set of data may either non-uniquely or uniquely identify the tag.
• the first packet may be an IR packet and the second packet may be an IR packet
• the tracking environment may be a clinical environment.
• the method may further include storing at least a portion of the second set of data in the tag to obtain stored data.
• the method may still further include modulating a third carrier signal with a third packet including the stored data to obtain a modulated third signal.
• the method may further include transmitting from the tag to a device other than the nearest sensor the third signal.
• the third signal has a third precision and a third range within the environment.
• the tag may be a multi-modal tag.
• the first precision may be greater than the second precision and the first range may be shorter than the second range.
• the third packet may be an RF packet.
• the first precision may be greater than the third precision and the first range may be shorter than the third range.
• the first and second signals may be electromagnetic signals.
• the first signal may be an IR signal and the second signal may be an RF signal.
• the first signal may be a line-of-sight signal and the second signal may be a non-line-of-sight signal.
• the first, second and third signals may be electromagnetic signals.
• the first signal may be an IR signal and the second and third signals may be RF signals.
• the first signal may be a line-of-sight signal and the second and third signals may be non-line-of-sight signals.
• the method may further include validating the second packet prior to the step of determining.
• the tag may be battery-operated.
• a real-time system of locating a mobile object or person in a tracking environment includes a plurality of sensors located in the tracking environment.
• the system further includes a tracking tag wearable by the person or attachable to the object.
• the tag is programmed to at least partially perform the step of modulating a first carrier signal with a first packet including a first set of data to obtain a modulated first signal.
• the tag is further programmed to at least partially perform the step of transmitting to a sensor nearest the tag the first signal.
• the first signal contains the first packet and has a first precision and a first range within the environment.
• the tag is still further programmed to at least partially perform the step of repeating the steps of modulating and transmitting until a modulated second signal is received from the nearest sensor within a time period after the step of transmitting.
• the second signal contains a second packet including a second set of data and has a second precision and a second range within the environment.
• the tag is further programmed to at least partially perform the step of receiving the second signal within the time period.
• the tag is still further programmed to at least partially perform the step of demodulating the second signal to obtain the second packet.
• the tag is further programmed to at least partially perform the step of determining location of the tag within the environment based on the second packet of the received demodulated second signal.
• the tag may be further programmed to at least partially perform the step of storing at least a portion of the second set of data in the tag to obtain stored data.
• the tag may be still further programmed to at least partially perform the step of modulating a third carrier signal with a third packet including the stored data to obtain a modulated third signal.
• the tag may be further programmed to at least partially perform the step of transmitting to a device other than the nearest sensor the third signal.
• the third signal has a third precision and a third range within the environment.
• the tag may be further programmed to at least partially perform the step of validating the second packet prior to the step of determining.
• FIGURE 1A is a schematic overview diagram and key of a simplified sample facility or tracking environment and illustrating one embodiment of a method and system of the invention
• FIGURE IB is a diagram and key similar to the diagram and key of Figure
• FIGURE 2 A is a diagram and key similar to the diagram and key of Figure 1 A and particularly illustrating signal flow to and from RF and IR elements or devices;
• FIGURE 2B is a diagram and key similar to the diagram and key of Figure IB and particularly illustrating signal flow to and from RF and IR elements or devices;
• FIGURE 3A is a communications timing diagram for the small facility system of Figures 1A and 2 A;
• FIGURE 3B is a communications timing diagram for the extended system of Figures IB and 2B;
• FIGURE 4 is a block diagram flow chart illustrating acquisition and validation of location ID with regard to a tag and a sensor
• FIGURE 5A is a block diagram flow chart illustrating communications with a house system with respect to a tag and a gateway in a small facility;
• FIGURE 5B is a chart similar to the chart of Figure 5 A but with respect to a tag and a link in an extended facility;
• FIGURE 6 is a block diagram flow chart illustrating communications between a gateway and link(s);
• FIGURE 7 is a block diagram flow chart illustrating communications initiated by a tag switch event
• FIGURE 8 is a schematic block diagram illustrating a tag or badge constructed in accordance with at least one embodiment of the present invention.
• a method and system constructed in accordance with at least one embodiment of the present invention provides the ability to track staff, patients, or assets within a facility or tracking environment. This is accomplished through the use of badges or tags (used interchangeably herein) on the persons or objects needing to be tracked.
• FIG. 1A illustrates a sample facility installation where the gateway can be located such that the tags and diagnostic communications of the sensors can be received directly by the gateway. Sensors (the IR receivers and RF transceivers) are located in areas where location information is desired. Link modules are not needed.
• Figure IB illustrates a sample larger facility installation where link modules are used to extend the RF coverage.
• the gateway to the house data system is located so that the distances to the furthest devices are minimized.
• Sensors (the IR receivers and RF transceivers) are usually located one in each area to be identified.
• the link modules are placed in locations where they provide the necessary coverage to pick up tags and the relay the diagnostic signals of the sensors.
• FIG. 2A illustrates the RF and IR components of the RTLS system for a smaller facility. They are shown identifying their IR and RF communications capabilities.
• Tags have IR transmit and bidirectional RF capability and can communicate with sensors and a gateway.
• Sensors have IR receive and bidirectional RF capability and can communicate with tags and a gateway.
• the gateway has bidirectional RF capability for communicating with tags and sensors along with a network interface which is typically ethernet to communicate with the house data system.
• FIG 2B illustrates the RF and IR components of the RTLS system for a larger facility and are shown identifying their IR and RF communications capabilities.
• Tags have IR transmit and bidirectional RF capability and can communicate with sensors and links.
• Link modules have bidirectional RF capability only and are capable of communicating with tags, sensors, and a gateway.
• Sensors typically have IR receive and bidirectional RF capability.
• the gateway has bidirectional RF capability for communicating with links along with a network interface which is typically ethernet to communicate with the house data system.
• Figure 3A illustrates, based on an event such as from a timer or switch closure, a tag which transmits a short IR packet consisting of a start bit and a few other bits to convey data such as mode and/or error checking.
• the IR transmission length can be on the order of 4-8 milliseconds or less compared to systems where the data bits required to convey the serial number require a transmission length more on the order of 70-80 milliseconds or 10% or less of what was required with the serial number embedded. This has a number of important benefits:
• the tag acquires its location by sending a short IR message and receiving an RF transmission from a nearby sensor. If no response is received after a predetermined delay, the tag will retry. This process is continued on a predetermined schedule by a tag so that it is always up to date with the location ID (sensor serial number) that it is nearest. On an independent schedule, the tag can pass on its location ID to a gateway to communicate to the house data system its current location. Previous designs required this to occur as part of the communication with the sensor. This architecture permits it to occur only as needed such as on location change which results in fewer RF transmissions reducing the likelihood of collisions and increasing battery life.
• Figure 3B illustrates in a larger facility where RF range may be a problem.
• Link modules may be employed to enable tags and sensors to communicate with the gateway at a much greater distance.
• the process of the tag in acquiring location information (nearest sensor's serial number) is the same as with a smaller system but the link modules enable communication at a greater distance by repeating the tag communications to and from the gateway.
• the flow chart of Figure 4 demonstrates the process by which the tag acquires and validates its location ID.
• the tag sends a short IR packet to the sensor(s). It expects an RF message back from the nearest sensor. A timeout is employed to prevent the tag from waiting an unreasonable amount of time and if no message is received the tag will, after a predetermined time delay, try again with another IR packet.
• the tag conditions its acceptance as a location by comparing with previous location IDs. If the same location ID is not received n times in a row, it will not accept the new location ID.
• This validation process is desirable because the possibility exists that two tags in adjacent areas might coincide time-wise in communicating with different sensors and the sensor RF message that a tag receives could be from a sensor in a nearby area and not the one it sent its IR packet to.
• the validation process consists of receiving a location ID from a sensor and doing this several times with varied programmable delays so that no two tags would be communicating successively with the same sensor to make it through the validation process. If a tag fails to communicate or validate with any sensor within a predetermined number of attempts, the location ID will be set to a value such as zero to designate that no validated location information has been received by the tag.
• the validation process is the same whether or not link modules are used to extend communication with the gateway.
• Figure 5A illustrates that in a smaller facility at predetermined time intervals the tag transmits an RF packet to the gateway. It looks for a return gateway RF packet and if not received within a predetermined amount of time it delays and retries the process. When it receives a gateway packet, it extracts its message or acknowledgment and acts on the message or goes to sleep if acknowledged.
• Figure 5B illustrates that, similar to the smaller facility in a larger system, link modules are used to extend the range.
• the tag transmits an RF packet to a link module.
• the link module passes this on to the gateway and receives a return message.
• the tag waits for an acknowledgment or message and retries with the link module if it does not receive one. It acts on the message or goes to sleep if acknowledged.
• Figure 6 illustrates that, for extended range systems, the gateways and tags communicate by going through link modules which receive the tag messages and pass them on to the gateway and receive the gateway messages and pass them on to the tags.
• Figure 7 illustrates that if a switch on the tag is closed or certain other events happen on the tag, the tag will, after a predetermined delay, send a message to a link(s) or in the case of a smaller facility (no links) directly to a gateway. It will then wait for a return message or acknowledgment. If the exchange is not successful, it will retry after a predetermined delay until successful.
• Figure 8 illustrates a block diagram showing the major elements of a tag.
• the "brains" of the tag is a microprocessor which composes and sends the IR transmit packets and composes, sends and receives the RF packets. It also interacts with a motion detector (to reduce tag functionality during inactivity for battery conservation and reduced IR/RF traffic), switch(es), an RF transceiver, an IR transmitter, displays messages on an LED or LCD, and provides power management.
• a badge containing an IR transmitter and an RF transceiver at programmable intervals sends a short infrared packet which is picked up by a nearby sensor which includes an IR receiver and an RF transceiver, among other things.
• This infrared packet consists of a unique bit pattern, some of which may be an error detection bit(s) such as parity, checksum or CRC for the packet.
• One or more of the bits of the badge serial number may also be included in the packet to help reduce the chance of a misidentification and subsequent need for retry.
• An additional bit or more may be also employed to convey to the sensor a particular RF channel(s) to be used in responding or other mode controlling functionality.
• the IR packet is non-unique for all badges and in its more advanced form is unique to each badge.
• the sensor upon receiving a badge IR transmission, responds by transmitting an RF packet in part consisting of the sensor serial number (its ID).
• the exact time occurrence of this transmission from the sensor to the badge is not critical other than that it should occur within a reasonable period of time to preserve badge battery life since the receiver in the badge needs to be active until the RF transmission from the sensor has been received. If the RF transmission is not received within a reasonable interval, the badge will reinitiate the process.
• the badge Upon successful return of an RF transmission from the sensor, the badge extracts the sensor serial number and compares it with the last received sensor serial number.
• the badge accepts this sensor ID as its current location.
• the badge is responsible to keep track of the sensor ID as its location. Any time a sensor ID is received that is different from the previous, an additional exchange is desired for validation and it may be advantageous for the validation exchange to happen quicker than the normal period so as not to introduce any significant delay in the adoption of a new sensor location ID.
• the maintenance of location information in the badge allows it to pass this information on through a link to the gateway and house system on its own schedule and with a process independent of the sensors.
• the collision of the transmissions can cause neither to be received, in which case after a delay the badge retries. Different badges would have different retry delays to avoid subsequent sensor RF collisions.
• Badge IR transmissions can be very short and only single sensor RF transmissions are needed for the badge to learn its location.
• the identification process is robust in that any badge change in location should go through a validation process.
• the badge communication only needs to be a single one-way IR transmission to the sensor.
• Communication timing between the badge and sensor is not critical other than that it should occur within a reasonable time to not affect battery life.
• Latency between the badge and house system is optimal since the sensor is not a part of that process.
• the amount of activity on the part of the sensor is minimal resulting in less sensor current drain making its operation on battery power practical.
• the sensor may have bidirectional RF capability allows diagnostic and supervisory functions between the system and sensors independent of the badges.
• a user event such as a button press
• At least one embodiment of the present invention provides one or more of the following features:
• the short IR packet besides helping with battery life on the packet itself, also helps with minimizing collisions in two additional ways: one, because of the reduced packet length; and second, the frequency of occurrence of the IR packets can be reduced since the badges are aware of when they have successfully communicated with a sensor. In a one-way system where a badge never knows if it has been heard by a sensor, it therefore has to transmit on a more frequent basis. Being able to optimize the fire rate based on success helps both on collisions and also on battery life independent of the packet length factor.
• the badges are aware when they fail to communicate with a sensor for some period of time and can convey that information (the fact that they have not communicated with a sensor) to a link and gateway to the house data system.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• General Physics & Mathematics (AREA)
• Radar, Positioning & Navigation (AREA)
• Remote Sensing (AREA)
• Radar Systems Or Details Thereof (AREA)
• Alarm Systems (AREA)

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• 2010
  • 2010-07-28 US US12/845,228 patent/US8514071B2/en active Active
• 2011
  • 2011-07-27 WO PCT/US2011/045461 patent/WO2012015870A1/en active Application Filing
  • 2011-07-27 EP EP11813078.0A patent/EP2599061A4/en not_active Withdrawn
  • 2011-07-27 BR BR112013001820A patent/BR112013001820A2/pt not_active IP Right Cessation
  • 2011-07-27 AU AU2011282821A patent/AU2011282821B2/en not_active Ceased
  • 2011-07-27 CA CA2801364A patent/CA2801364C/en active Active
  • 2011-07-27 MX MX2013001140A patent/MX2013001140A/es active IP Right Grant

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